linux-kernel - Re: [PATCH v4 1/2] kallsyms: Always initialize modbuildid on ftrace address

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Message-ID: <20260107144434.233c1c15@gandalf.local.home>
Date: Wed, 7 Jan 2026 14:44:34 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Maurice Hieronymus <mhi@...lbox.org>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
 andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com,
 song@...nel.org, yonghong.song@...ux.dev, kpsingh@...nel.org,
 sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, mhiramat@...nel.org,
 mark.rutland@....com, mathieu.desnoyers@...icios.com,
 georges.aureau@....com, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] kallsyms: Always initialize modbuildid on ftrace
 address

On Sat, 20 Dec 2025 19:18:37 +0100
Maurice Hieronymus <mhi@...lbox.org> wrote:

> modbuildid is never set when kallsyms_lookup_buildid is returning via
> successful ftrace_mod_address_lookup.
> 
> This leads to an uninitialized pointer dereference on x86 when
> CONFIG_STACKTRACE_BUILD_ID=y inside __sprint_symbol.
> 

Nothing should be getting a buildid from the ftrace kallsyms lookup.

This code is used to find the names of init functions of modules after
those init functions have been freed. Nothing but ftrace should be looking
for these addresses, and ftrace doesn't care about buildids.

-- Steve